Idris Elba as Nelson Mandela and Naomie Harris as Winnie Mandela in 'Mandela: Long Walk to Freedom.' / Keith Bernstein, The Weinstein Co.

by Claudia Puig, USA TODAY

by Claudia Puig, USA TODAY

Sometimes it's the most remarkable and heroic figures whom movies can't seem to get right.

Such is the case with Mandela: Long Walk to Freedom (* * ½ out of four; rated PG-13; opens Friday in select cities), a biopic that is more dutiful than illuminating.

Earnest and ambitious, the film suffers from trying to squeeze in too many milestones of Nelson Mandela's long life as he worked to end the oppressive regime of apartheid in South Africa. But the talent of the lead actors lends it heft, particularly the commanding performance of Idris Elba as Mandela.

Elba captures Mandela's activist spirit as well as his vocal cadences, though he resembles him less than Morgan Freeman and others who have played him in movies.

As it is based on the subject's autobiography, Mandela should be more than well-meaning. But what ends up on the screen lacks the shading and complexity one would expect of the story of the 95-year-old South African anti-apartheid revolutionary and former president.

The biopic covers half a century, including Mandela's teen years, his time as a Johannesburg attorney, his involvement in anti-colonial politics, the 27 years he spent in a remote prison and his election in 1994, when he became South Africa's first black president. His commitment to the anti-apartheid cause is striking because of what we know of him from real-life news accounts. But the film does little to deepen our sense of the man behind the kindly, open face.

Elba is the reason to see the film. He powerfully conveys Mandela's charisma and impassioned dedication.

The film wisely doesn't sweeten Mandela's personal life. His womanizing, failed first marriage and strained relationship with his son are portrayed with some complexity.

But director Justin Chadwick rarely presents Mandela as a flesh-and-blood mortal. Instead, he sanctifies him. Telling details are bypassed in favor of too many fiery speeches.

Naomie Harris is convincing as the spirited Winnie Mandela, Nelson's wife from 1958 to 1992. Her story was less effectively covered in Winnie, a film starring Jennifer Hudson that came out in September. Harris' chemistry with Elba is evident. While the couple's eventual estrangement is treated somewhat cursorily, we get a sense of how they grew apart because of their differences in outlook (he was more moderate) as well as their long separation during the nearly three decades he was imprisoned. Their outrage at the country's institutionalized racism took markedly different forms. An increased focus on their diverging tactics might have made this a more intriguing film.

Instead, Winnie is off-screen for sizable periods, and her evolution from loyal spouse to unfaithful militant leaves the viewer with questions.

While meaningfully portraying the eventful life of a great leader is no doubt a huge challenge, the story could have been more tightly focused and less surface-skimming.

At times, it feels like a listing of key events in Mandela's life, rather than an insightful, humanizing portrait.

And in the final third, everything feels rushed.

Mandela's is undeniably a fascinating life, and given his age and recent ill health, the time is right for a comprehensive look at his significant contributions to human rights.

But the cinematic retelling would have benefited from deeper illumination and perspective.

It's not hard to be affected by a film chronicling the accomplishments of such a heroic figure. But Mandela deserves something more profound, layered and dimensional, much like the man himself.